Single-ion magnet behaviour in [U(TpMe2)2I]

Abstract

[U(Tp(Me2))(2)I] exhibits at low temperatures single molecule magnet (SMM) behaviour comparable to its bipyridine derivative and related single ion U(III) complexes recently reported as SMMs. The trend of variation of the energy barrier for the magnetic relaxation in these compounds is well reproduced by quantum chemistry calculations.

Molecular single-ion magnets based on lanthanides and actinides: Design considerations and new advances in the context of quantum technologies

“…The difference in behaviour is ascribed to the weaker ligand field felt by the U III ion due to a softer electron donating ability of the bipy ligand, and longer U-N distances [30]. The precursor of this complex, [U(Tp Me2 )2I] (72) showed SIM behaviour under a small applied field, with Ueff = 30 K (21 cm −1 ), which is slightly larger than that of 71 [122]. Notably, the calculated energy gaps of 146 and 138 cm −1 for 71 and 72, respectively, again overestimate the Ueff values.…”

“…Indeed, some examples of 5f-SIM systems based on U 3+ (5f 3 , J = 9/2) [24,27,28,30,[118][119][120][121][122][123], and U 5+ (5f 1 , J = 5/2) [25,26] ions have been reported in the last few years. Both are Kramers ions (S = half integer) with large values of angular momentum, J, which are guaranteed to possess a doubly-degenerate mJ ground state-an important requirement in SIM research.…”

Radical ligand-containing single-molecule magnets

“…Additionally, in contrast to lanthanides, actinides provide a wide range of accessible oxidation states [320]. However, only a few actinide complexes have been shown to exhibit slow magnetic relaxation, with nearly all of these being uranium complexes [343][344][345][346][347][348][349][350][351]. Nevertheless, despite the difficulties associated with handling of the more radioactive transuranic elements, neptunium and plutonium-based singlemolecule magnets have also been reported [352][353][354].…”

Field-induced single-ion magnetic behaviour in a highly luminescent Er3+ complex

“…At 1.6 K a clear opening of the magnetic hysteresis is observed as one moves away from zero field, revealing strong field dependence. The absence of coercivity can be due to an efficient quantum tunnelling of the magnetization occurring at zero field, probably caused by low symmetry components of the crystal field, as it was already observed in other mononuclear lanthanide [17,18,28] and uranium [29,30] compounds with SMM behaviour. At this temperature and up to 10 T, magnetization approaches a value of 7.9 μB, still far from the expected saturation value for a free Er 3+ ion.…”